Photolithography is a process commonly used in semiconductor fabrication for selectively removing portions of a thin film from or depositing portions of a film onto discrete areas of a surface of a semiconductor wafer. A typical photolithography process includes spin coating a layer of a light-sensitive material (commonly referred to as a “photoresist”) onto the surface of the semiconductor wafer. The semiconductor wafer is then exposed to a pattern of light that chemically modifies a portion of the photoresist incident to the light. The process further includes removing one of the incident portion or the non-incident portion from the surface of the semiconductor wafer with a chemical solution (e.g., a “developer”) to form a pattern of openings in the photoresist on the wafer. Subsequently, portions of the thin film on the surface of the semiconductor wafer can be selectively removed from or deposited onto the surface of the wafer through the openings of the photoresist mask. The photolithography process can be repeated to form layers of microelectronic features on or in the semiconductor wafer.
In the foregoing process, a new pattern must be aligned with patterns already on the semiconductor wafer before exposure. If the alignment of the new pattern is inaccurate, the new pattern may overlap and/or otherwise interfere with existing patterns on the semiconductor wafer to render the formed features inoperable. As a result, the alignment accuracy can directly impact product yields of the photolithography process. Moreover, the speed of the alignment procedure can directly impact the throughput of the photolithography process. Accordingly, several improvements for enhancing the accuracy and/or the speed of these methods and devices would be desirable.